1. Field of the Invention
The present invention relates to an optical information detection device for detecting the information of light incident into a double-mode channel waveguide by utilizing interference between 0th-mode light and 1st-mode light in the double-mode channel waveguide, and a mode interference type laser scanning microscope.
2. Related Background Art
In recent years, optical waveguides have received a lot of attention in various fields since an optical system can be rendered compact and lightweight using the optical waveguide, and is free from adjustment of the optical axis. The optical waveguides are classified into a single-mode waveguide (which guides light in a single mode) in which only 0th-mode light is excited on the basis of the difference between the refractive indices of an optical waveguide (core portion) and a substrate (cladding portion), and the width or refractive index distribution of the optical waveguide, a double-mode waveguide (which guides light in double modes) in which two mode light beams, i.e., 0th- and 1st-mode light beams are excited, and a multi-mode-waveguide (which guides light in multi modes) in which three or more mode light beams, i.e., 0th-, 1st-, 2nd-mode light beams, and the like are excited. In the double-mode waveguide and the multi-mode waveguide, a plurality of mode light beams are not always excited, and these waveguides are classified depending on the maximum number of mode light beams to be excited. For example, only 0th-mode light may be excited depending on the position or state of light incident into the optical waveguide.
As an application of such an optical waveguide to a new field, an optical information detection device which utilizes a mode interference phenomenon in a double-mode channel waveguide is known. This device is receiving a lot of attention from researchers in various fields as an effective device which can be used in various applications. The basic principle of the optical information detection device and an application to a mode interference type laser scanning microscope are described in detail in H. Ooki and J. Iwasaki, Opt. Commun. 85 (1991) 177-182, and Japanese Patent Laid-Open Nos. 4-208913 and 4-296810. Also, an application to an optical pickup is described in detail in Japanese Patent Laid-Open No. 4-252444.